Where does “ꙗловица” come from?

ꙗловица (Church Slavonic) comes from Proto-Slavic jalovъ, from Proto-Indo-European jal- — bad.

Ancestry of “ꙗловица”, step by step

Step	Language	Word	Meaning
1	Proto-Slavic	jalovъ	idle; infertile, barren
2	Proto-Indo-European	jal-	bad